The present invention relates to a compressor system and, more particularly, to a rotary-type compressor system in which no oil is supplied into the operating space thereof.
In, for example, U.S. Pat. No. 4,529,363, a single-stage oil-free screw-type compressor of the aforementioned type is proposed which includes, inter alia, a precooler, a cooler, a transmission device, and a check valve, with the compressor system utilizing water as a medium for cooling the precooler and the cooler.
A disadvantage of the above-described rotary-type compressor resides in the fact that the compressor must use tap water or underground water as a medium for cooling the precooler and the cooler. Consequently, it is impossible to install such a system at a site or location where no tap water or underground water is available.
A further disadvantage of the above-proposed compressor system resides in the fact that, when changing the installation site of the system, the piping for the cooling water must be removed and reinstalled which is not only inconvenient but also somewhat expensive.
Cooling water, more particularly tap water, is corrosive and, since the precooler and cooler are made of a copper or aluminum material, they are subject to corrosion. A cooling water passage may become partially or completely blocked because of rust or sludge resulting from the corrosion of the precooler or the cooler. Consequently, it is necessary to carry out frequent inspection and maintenance of the system, including removal of the rust and sludge and cleaning of the passage.
Accordingly, an object of the present invention resides in providing an oilless rotary-type compressor system which is operable at a site where it is either difficult to supply cooling water or where the quality of water is poor.
Another object of the present invention resides in providing an oilless rotary-type compressor system which minimizes corrosion caused by the cooling medium to such an extent that no operational problems are experienced.
In accordance with advantageous features of the present invention, an oilless rotary-type compressor is provided which includes a radiator having a fan and a heat exchanger, with the radiator being connected through a piping or conduit system to a jacket of a compressor body and a precooler so that a heat transfer medium for cooling is sequentially circulated through the radiator, the jacket of the compressor body and the precooler.
Accordingly, by virtue of the features of the present invention, the radiator, the jacket of the compressor body and the precooler together form a circulation circuit through which the heat transfer medium for cooling is circulated, whereby it is possible to disperse heat generated by the compressor body and the precooler without a cooling medium such as, for example, water. An aqueous solution of non-polluting propylene glycol, an approved food additive, is employed as a heat transfer medium so as to avoid exposing a user of the system to harmful effects even if the system should develop leaks.